1. Field of the Invention
The present invention relates to an image forming apparatus in MFPs (Multi-Function Peripherals) as digital composite machines, copiers and printers, and particularly, to an image forming machine which suppresses an increase in temperature.
2. Description of the Related Art
Generally, in an image forming apparatus in MFPs, copiers and printers, there is used a fixing equipment to form a toner image on paper and to fix this toner image on paper. The fixing equipment has a heat roller for heating and a pressure roller, and an unfixed sheet is transported between this pair of rollers.
In such a fixing equipment, in order to prevent an abnormal increase in surface temperature of the heat roller, the temperature of the heat roller is detected by arranging a temperature detection element such as a thermistor and is controlled to be maintained within a predetermined temperature range based on this detection result.
In Jpn. Pat. Appln. Laid-Open Publication No. 7-325500, there is disclosed a fixing equipment which has a heat roller and a pressure roller, a plurality of halogen lamp heaters being provided in the heat roller. In this example, the plurality of halogen lamp heaters are rotatably provided in the heat roller, and in a standby mode where the heat roller is stopped, the plurality of halogen lamp heaters are rotated to maintain the surface temperature of the heat roller equal. In addition, a plurality of thermistors to detect the temperature are arranged on the heat roller and the heating conditions of the halogen lamps are controlled based on the temperature detection results by those thermistors.
However, in the conventional image forming apparatuses and in the example of the above Jpn. Pat. Appln. Laid-Open Publication, there is a problem that the temperature cannot be detected accurately and the fixing equipment is abnormally heated if the element to detect the temperature of the fixing equipment is broken or if the connector to connect the temperature detection element to a control circuit is disconnected.
The present invention may provide an image forming apparatus which controls the temperature of the fixing equipment to prevent the abnormal heating of the fixing equipment and to improve the safety thereof.